An improved hammer for hammer mills

ABSTRACT

A hammer for a hammer mill, cast from austenitic manganese steel, is cast with a pad of extra metal surrounding the eye, the extra metal being work hardened to inhibit stretching of the eye when the hammer is revolved with its supporting rod which fits the eye diameter.

United States Patent 11 1 Fabert, Jr.

[111 3,738,586 June 12, 1973 1 IMPROVED HAMMER FOR HAMMER MILLS [75] Inventor: Herman A. Fabert, Jr., Homewood,

[73] Assignee: Abex Corporation, New York, NY.

[22] Filed: July 14, 1971 [21] Appl. No.: 162,358

52 us. Cl. 241/195 51 1m. 01. B02c 13/28 [58] Field of Search 241/194, 195, 196,.

[56] References Cited UNITED STATES PATENTS 2,566,758 9/1951 Anderson 241/197 3,278,126 10/1966 Ratkowski 241/195 2,237,510 4/1941 Tankersley 241/195 2,244,577 6/1941 Schreiber 241/195 Primary Examiner-Robert L. Spruill Attorney-Kinzer & Dorn [57] ABSTRACT A hammer for a hammer mill, cast from austenitic manganese steel, is cast with a pad of extra metal surrounding the eye, the extra metal being work hardened to inhibit stretching of the eye when the hammer is revolved with its supporting rod which fits the eye diameter.

2 Claims, 5 Drawing Figures Patented June 12, 1973 FIG. 3

FIG.|

FIG. 5

INVENTOR. HERMAN A. FABERT, JR

AT ORNEYS FIG. 4 BY M, db/9W IMPROVED HAMMER FOR HAMMER MILLS This invention relates to the construction of a hammer for installation in a hammer mill.

The typical hammer mill, used to comminute rocks, scrap metal chunks and the like, includes a large rotary driven ring or disc supporting circumferentially spaced rods each of which fits the eye of a hammer to support the hammer and whirl it with the ring. The working forces are of large order. Resultantly, there is a pronounced tendency for the eye of the hammer to stretch due to the play of centrifugal forces between the hammer eye and its support rod. Thus, the eye is distorted, the hammer wobbles, vibrations ensue, and the mill must be shut down for hammer replacement.

The problem is especially acute with hammers of austenitic manganese steel, because of its inherent ductility.

The problem has been known for more than 40 years. In U.S. Pat. No. 1,760,097 (tiled in 1928) it is stated Oscillation of the hammers upon the rod on which they are pivoted causes wear in the eye and on the rod. The patentee proposed that the problem be solved by altering the center of gravity. He did this by enlarging the hammer head, but did not observe that the additionalweight so added produces more strain on the mill as can be well imagined from the increased weight at the end of the whirling hammer. Under my invention, there is no change in the center of gravity and essentially no increased strain on the mill, and the achievement of this is an object of the present invention.

The very nature of austenitic manganese steel contains the clue to avoiding eye distortion of a hammer. The clue is that if the hammer is cast from austenitic manganese steel, and if it so cast as to present a thickened ring or pad of extra metal surrounding the extremities of the eye, the extra metal may be work hardened. The effect is an eye which is hardened at the extremities. Since the extremity is hardened, the metal resists flow to that extent, which is to say that stretching is inhibited proportionally. It is, therefore, a further object of the present invention to cast a hammer from austenitic manganese steel with an integral ring of extra metal at each end of the eye, the ring being work hardened.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawing, which by way of illustration, show embodiments of the present invention and the principle thereof and what is now considered to be the best mode contemplated for applying that principle. Other embodiments of the invention embodying the same or equivalent principle may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention.

In the drawing:

FIG. 1 is a sectional view, partly diagrammatic, of a typical hammer mill;

FIG. 2 is a perspective view of one form of hammer constructed in accordance with the present invention;

FIG. 3 is partial sectional view of the hammer shown in FIG. 2;

FIG. 4 is a plan view of another form of hammer constructed in accordance with the present invention; and

FIG. 5 is a sectional view of the hammer shown in FIG. 4.

FIG. 1 shows a typical hammer mill wherein rocks, scrap metal chunks and other burden oflarge size is to be crushed to a smaller size. In doing this, resort is had to a hammer support ring 12 fixed to a drive shaft 13 for rotary movement.

The support ring or disc 12 carries four hammer support rods 15 each supporting, pivotally, a hammer 17.

These hammers 17 are whirled or revolved within the mill. The impacting face 18 of each hammer follows a circular path opposite a grate ring 20 characterized by spaced bars or ribs 21, the spacing therebetween defining slots 22 through which the comminuted material is discharged for collection in the discharge bin 25.

As noted above, the hammers are pivotally mounted on the support rods or shafts l5 so that there may be free swinging movement of the hammers in the course of operation. This is always so. The working forces involved are of very high order, especially the play of centrifugal forces between the support rod 15 and the eye or opening in the hammer shaft enabling the hammer to be mounted thereon. The forces are so large that stretching or distortion of the eye is a frequent, and in fact normal, reason for shutting down the mill to replace the hammers. It can be readily visualized that when the eye is distorted, the hammer will wobble producing unacceptable vibrations within and strain on the mill.

Hammers of the kind involved may be of variant shape. One such form, as shown at 30 in FIG. 2; geometry is unimportant, but for purposes of definition the hammer 30, under the present invention, is cast entirely of austcnitic manganese steel and includes a hammer head 31 and a shank 32. The shank is formed with a relatively large eye 33 for the purpose mentioned above.

Ordinarily hammers of the kind involved, cast from austenitic manganese steel, will have a Brinell hardness of -220 BHN and a nominal yield strength of about 50,000 psi, too low to preclude stretching which progresses to a degree leading to failure at the eye.

Under the present invention, the hammer is cast entirely of austenitic manganese steel with thickened rings or pads 35 continuous about the end openings of the eye 33. The rings 35 project axially from the eye, characterizing the thickened section, which in plan has the shape of torus.

After the casting has been taken from the heat treating furnace the thickened pads or rings 35 are work hardened, as by hammering, to a Bl-IN value of 440-480, with corresponding increase in yield strength. During work hardening, some metal from .the pads may flow into the interior of the eye, but any unacceptable dimension can be restored by a grinding operation typically performed on manganese steel.

Preferably the inner diameter of the extra metal rings is chamfered at 36 to provide an outwardly sloped radial face which facilitates application of the hammer blows, since the important aspect is that the areas around the ends of the eye be hardened and not necessarily the interior of the eye. Resultantly the effect is that the end openings of the eye 33 have approximately double the hardness of the rest of the casting. There is in effect scarcely any allowance for metal flow or duetile distortion, so that the integrity of the eye diameter remains virtually constant. On the other hand, I retain all of the advantages of unhardencd austenitic manganese steel, at the impacting face and sides of the hammer, known to provide distinctive wear life over metals having higher strength.

Another form of hammer, a so-called ring hammer suitable for use, is identified by reference character 40 in FIG. 4. This is for the purpose of projecting the realization that hammer mill hammers are of variant geometry. The hammer 40 is one piece, cast entirelyof austenitic manganese steel, and lugs 41 represent a plurality of hammer elements. Again, the eye 42, at the extremities, is cast with rings 44 of extra metal of the form described above, work hardened for the purpose already explained.

I claim:

1. In a hammer for a hammer mill wherein the hammer includes a shank formed with an eye enabling the hammer to be mounted on a supporting rod for revolving movement within the mill, the improvement wherein the hammer is cast from austenitic manganese steel metal with a ring 'of extra integral metal surrounding and projecting axially of the eye on each side of the hammer, the extra metal being work hardened to a Bl-lN hardness value which is approximately twice the hardness value of the remainder of the hammer to thereby inhibit stretching due to centrifugal forces exerted on the eye when the hammer is revolved.

2. A hammer according to claim 1 in which the extra ring of metal is chamfered at the eye diameter to provide an outwardly sloped radial face to facilitate work hardening. 

1. In a hammer for a hammer mill wherein the hammer includes a shank formed with an eye enabling the hammer to be mounted on a supporting rod for revolving movement within the mill, the improvement wherein the hammer is cast from austenitic manganese steel metal with a ring of extra integral metal surrounding and projecting axially of the eye on each side of the hammer, the extra metal being work hardened to a BHN hardness value which is approximately twice the hardness value of the remainder of the hammer to thereby inhibit stretching due to centrifugal forces exerted on the eye when the hammer is revolved.
 2. A hammer according to claim 1 in which the extra ring of metal is chamfered at the eye diameter to provide an outwardly sloped radial face to facilitate work hardening. 